Spring strip



Dec. 18, 1951 wm 2,578,958

SPRING STRIP Filed NOV. 16, 1945 I N V EN TOR. 774/7345 Ffl/zkz era Patented Dec. 18, 1951 NT F E SPRING STRIP Thomas F. Winters, Detroit, Mich., assignor to No-Sag Spring Company, Warren Township, Mich., a corporation of Michigan Application November 16, 1945, Serial No. 629,094

2 Claims. 1

This invention relates to springs, and particularly to a spring of the sinuous type having an arcuate and straight portion to provide a predetermined contour when a surface formed by the springs is occupied.

It has been the practice heretofore in the art to form springs from wire by bending the wire back and forth in zigzag formation having oppositely disposed adjacent loops joined by straight portions such as illustrated in the patent to Karl Kaden, Reissue 21,263. small art along its longitudinal dimension so as to provide inherent resistance against deflection when the ends are extended and anchored to dispose the strips upon an arc of large radius when forming a load supporting surface. When a load was applied to the spring strips the spring naturally tended to foreshorten and usually formed a pocket in the central portion which assumed a hammocking effect when a substantial load was applied thereto.

The present invention pertains to a similar type of spring having only a portion of the strip provided with an arc of small radius with one end portion left straight. A substantial portion of the spring offered resistance against downward deflection when the ends of the spring were extended and anchored to opposite sides of a frame. When a load is applied to such a spring, the unarched portion offering no resistance to deflection would readily deflect and form a pocket at the spring end. This spring end was anchored to the rear frame member so that when a surface formed by a plurality of the springs was occupied, a pocket was formed at the rear edge of the seat and the surface is arched upwardly therefrom to form a downwardly presenting arched portion between the center and the front edge of the seat. This provides a reverse contour to the occupied surface which equally distributes the load over the occupant, eliminating the load concentration which would otherwise occur. This predetermined contour provides unit loading over the occupied area and is produced by the elimination of the arcuate set portion in the end of the spring strips anchored at the rear of the seat.

Accordingly, the main objects of the invention are: to provide a spring strip having a portion set on an arc along the longitudinal dimension and an end portion left straight for the purpose of controlling the contour of the spring when occupied; to set a portion of a spring strip on an arc of small radius to have the portion offer resistance against deflection with an adjacent end portion left straight; to set a spring strip along its The strip was set on a.

longitudinal dimension in such manner as to have a surface formed from a plurality of the strips assume a predetermined desirable contour which uniformly distributes the load when the spring strips are occupied; and, in general, to provide a spring strip which produces a predetermined desirable contour when occupied which is simple in construction and economical of manufacture.

Other objects and features of novelty of the invention will be specifically pointed out or will become apparent when referring, for a better understanding of the invention, to the following description taken in conjunction with the accompanying drawing, wherein:

Figure l is a view in elevation of a sinuous spring strip embodying features of this invention;

Fig. 2 is a side view of the spring illustrated in Fig. 1;

Fig. 3 is a sectional view of a frame having the spring strip illustrated in Figs. 1 and 2 applied thereto; and

Fig. 4 is a view of the structure illustrated in Fig. 3 when the surface formed by the spring strips is occupied.

Referring to Figs. 1 and 2, a sinuous spring strip I ll is illustrated which was formed sinuously from wire into adjacent oppositely disposed loops H and i2 which are joined together by straight portions l3. This spring is illustrated, described and claimed in the Karl Kaden reissue patent above mentioned. The spring of the application was rolled on a mandrel of small diameter to set the spring on an arc of small radius to provide an inherent resistance against deflection when the ends are supported across a frame to have the spring disposed on an arc of large radius.

The present spring II] has a major portion [5 rolled upon an arc of small radius and has an end portion [6 left unrolled. The portion I5 provides resistance against deflection while the portion l6 lacks such resistance. The resistance against deflection is necessary in this type of spring to prevent the spring from passing beyond the plane in which the ends are supported and assume an upwardly presented arch which has no inherent force to return the strip to the position above the plane of the supported ends. When the resistance against deflection is incorporated in the spring strip by setting the spring on a small diameter, the load deflecting the spring through and beyond the plane of the supported ends will be opposed by the force inherently provided in the spring. When the load is removed, the spring strip will be returned to its original arched position above the plane through the supported ends. The major portion of the spring strip l0, being provided with the arc of small radius, will have suiiicient force to return the strip to its arched position I! above the frame l8 to'which the ends are secured by suitable clips IS. The unset end portion I6 is secured adjacent to the rear end of the frame 18 and when a load is applied to a series of the spring strips I which'are secured in aligned relation across the frame l8, the rear end portion IE will immediately deflect. After the complete load is applied to the plurality of spring strips ID, a predetermined desirable contour 2| will be assumed by the springs, as illustrated inFig. 4. Such a contour provides a uniform distribution of the spring pressure and prevents a concentration of the pressure which occurs if the desirable contour is not produced when the spring surface is occupied. The inherent resistance against deflection in the portion l5 of the strip is sufiicient to return the strip to the original arched position,as illustrated in Fig. 3, when the spring strips aredeiiected below the plane of theframe.

Whatisclaimed-is:

l. Aspring strip .for a seat cushion "made of wire bent back and forth ..in sinuous formation having adjacent oppositely v disposed *loops joined by straight'portions, the major length of said strip from one end "beyond the center thereof when the ends of the strip are unsecured being seton an arc of predetermined radiusalongthe length -of the strip --with the remaining portion retained straight in extensionof said set portion, a seat frame having'a front and-rear supporting element, and means -for securing a plurality of the springs to'saidelements with the end of the set portion secured to the front element and the end of the straight portion secured to the rear element with the set portion disposed on an arc of greater radius, whereby the rear straight portion of the strips may deflect a greater amount under load than said set front portion thereof.

2. A spring strip adapted to be disposed across a frame of a cushion when the end portions are extended and secured to oppositely disposed members thereof for supporting .a load, said strip being made of wirebent back and forth in sinuous formation having adjacent oppositely disposed loops joined by straight portions, the major length .of said strip from one end portion beyond the .center thereof when the end portions of the strip are unsecured being set on an arc of predetermined radius along the length of the strip with the remaining portion retained straight in extensionof theset portion, said set portion being disposed on an arc of larger radius and provi'din greater resistance to deflection than said straight portion when the end portionsare extended imposition to be securedto aframe.

THOMAS F. WINTERS.

REFERENCES GIT-ED "The following references are of record'in the file of this patent:

UNITED STATES PATENTS 

